Families caring for young people with mental retardation face major burdens of care if the young person also has emotional and behavioural problems. Serious mental health problems are 2-3 times more common in young people with mental retardation, which apart from the personal distress and loss opportunity it causes the child and family, is also a major cost to our community. This project is intended to assist young people and their careers by providing new information about the factors contributing to these mental health problems and how they develop over time. The project makes use of the existing internationally unique epidemiological longitudinal study (the Australian Child and Adolescent Development Study ACAD) which has followed a group of young people with mental retardation aged 4-18 for the last eight years, from childhood through adolescence as they move into young adult life. The ACAD study has collected an extensive range of biopsychosocial data on these young people and their families. This project will examine the unique database produced by the ACAD study using state-of-the-art statistical techniques in to order to elucidate the biopsychosocial risk and protective factors relating to the progression and development of mental health problems in this under researched and under serviced population. It is expected that the results of such analyses will directly contribute to the development of appropriate intervention and prevention programs.